This invention relates to a control system for controlling the working depth of an implement pulled by an agricultural vehicle.
The quality of operation of conventional hitch control systems, such as draft and/or position-responsive systems, may vary, depending upon the particular implement being used or upon the particular soil conditions encountered. For example, a particular control system with a fixed gain may operate sluggishly under relatively loose soil conditions, whereas, the same control system may cause undesirably rapid, violent or unstable hitch and implement motions when working in relatively stiff soil conditions. One solution would be to provide a variable gain control which can be adjusted by the vehicle operator to optimize performance under various conditions. However, it would be desirable to provide hitch or implement control systems which automatically compensates for varying conditions without increasing the level of skill or effort required of the operator. One such automatically compensating system is described in a "Model Reference Adaptive Control System" in U.S. Application, Ser. No. 405,835, (now U.S. Pat. No. 4,495,577) filed Aug. 6, 1982 and assigned to the assignee of the present invention. This "Model Reference Adaptive" control system requires an operator-adjustable draft setting or load command knob in addition to a position command lever. It would be desirable to provide an automatically compensating implement control system which is simpler with respect to the number of operator controls required and with respect to algorithm complexity.